A multiparametric approach to a study of the penetration phase of Trypanosoma cruzi-vertebrate cell interactions is utilized in order to develop a mathematical model of the phenomenon. The effects of varying physiologic parameters will be studied in this system and compared with other host-parasite systems such as Toxoplasma gondii-vertebrate cell interactions. Low-light-level video techniques have been expanded to include clinical applications such as studies of epileptiform seizures and myocardial infarction. Video microscopy techniques have been expanded to include the semiautomated analysis of microtiter plates.